When Ledda makes a phone call at a park, in the background is an Opel Corsa C. It has its taillights at the side of the windows. The first car that had this type of light was a Ford Focus in 1999. The Opel is build after 2000.
Some of the cars carry European-style license plates (full width, with a blue European mark on the left side - most clearly seen on the Mercedes cab that Ledda rides in). These were not yet introduced in 1995, the time the movie is set.
Bieke's father who gets shot resisting arrest at the beginning of the film, is clearly shot on his left side of the chest. But in the shot right before he lays still, we see the gunshot wound on the other side, then it flips back again when he's down.
When Ledda meets Bieke and her dog waterside, note how there is a boat in the background, behind Ledda. The view whips back and forth, and the boat is gone. The view whips back and forth again, and the boat is back. This was discovered one day before the DVD release, when the commentaries were being recorded, the director swore and said "That (...) boat did a Copperfield!"
Throughout the movie, the laser on Ledda's pistol is unsynchronized. In wide shots, he turns it on or off as appropriate (when hiding, he is not projecting a red light) but in all closeups the laser is on.
The laser mounted to Ledda's Beretta is not in a consistent position. Laser mounts of this era are difficult to install and it appears there are two prop guns. One has the laser mounted properly, the other has it pointed down at a 5° angle (which would make it useless for aiming). In closeups, the two are switched between in single scenes, so this is clearly a mistake, and does not indicate the character dropped the gun and misaligned the laser at some point, for example.
Near the end, when Ledda helds the doctor hostage, police tracks his actions on a monitor with USB-connection (we get to see the USB-sticker clearly several times). The movie is set in 1995. Although Compaq, DEC, Microsoft, and NEC defined the USB port in 1993, standards were approved by the group only in 1996, and the first implementation of USB did not occur until 1998.
The goof item below may give away important plot points.
1hr 52min into the movie, the hitman holds the two cops hostage in a car (just before he gets shot). He's holding a Browning HP35 pistol which flicks alarmingly between being cocked and uncocked. Note that this Browning is "single action" - pull the trigger on an uncocked Browning and nothing will happen.